Please note the distinction between "users" and "threads". There is no real limit on the number of active users for Tomcat unless you implement a Domain that keeps a tally and simply bounces logins after the limit has been reached.
The limit on threads, however, is controlled by server.xml, and that restricts the maximum number of concurrent requests that Tomcat will handle.
Since a web client typically can run several request threads concurrently (this helps in things like loading images), this means that the momentary "concurrent maximum users" limit can potentially be LESS than the thread limit, even though the long-term number of users may vastly exceed the thread limit.
Customer surveys are for companies who didn't pay proper attention to begin with.
subject: number of users that can access site parally